Chatot, The Music Note Pokémon. It mimics the cries of other Pokémon to trick them into thinking it's one of them. This way they won't attack it. It can learn and speak human words. If they gather, they all learn the same saying. Its tongue is just like a human's. As a result, it can cleverly mimic human speech.

Overview

Chatot is a unique little bird with an even more unique gimmick. Up until XY, Chatot was the only Pokémon to be banned from official formats alongside mascot legendaries and event Pokémon. However, rather than being banned for being too powerful, Chatot had its signature move Chatter to blame, which relied on yelling into the microphone to alter its cry into anything you want and ultimately increase the chance to confuse an opponent. While altering its cry into an indistinct mess is no longer possible in 6th Gen, Chatot's signature has been generously compensated with an obnoxious guaranteed confusion rate, with a bonus of no longer causing it to be banned in official formats. However, unfortunately for Chatot being a walking microphone doesn't help much in the big scary world of dragons, lava monsters and washing machines, and its subpar stats certainly don't help it. Not much has changed for Chatot throughout the generations either, until Gen 6 blessed it with a shiny new toy in the form of the powerful Boomburst. While this alone does nothing to fix Chatot's glaring flaws it does give the little parrot an incredibly useful STAB move that Pokémon like Pidgeot can only dream of learning. Chatot also has a fair few usable moves it can run such as Heat Wave and Nasty Plot so not everything is bad news for the little parrot. However, at the end of the day Chatot is just a fun little gimmick that will struggle to find its way onto any serious team. Positives
+Normal/Flying provides decent neutral STAB coverage, hitting everything bar Rock and Steel for at least neutral damage.
+Base 92 Special Attack is passable, and an acceptable base 91 Speed puts it just above Pokémon like Kangaskhan.
+Access to the rare and powerful Boomburst sets it apart from other Normal types, giving it a 140 base power STAB move with no drawbacks. If you're using Chatot for any reason at all, you better be using this move.
+Chatter, while only having 65 base power, gives Chatot a unique Flying STAB that is guaranteed to confuse the opponent.
+Moves like Nasty Plot, Encore and Heat Wave give the little parrot some nice options to play around with.

Negatives
-Chatot's defenses are painfully bad even for an offensive Pokémon. You aren't going to be taking even resisted hits very well with 76/45/42 bulk so good luck switching that into something safely.
-A weakness to Stealth Rock hurts its already low survivability to incoming attacks.
-Base 65 Attack is very weak, but Chatot lacks any notable physical moves besides U-turn anyway so that's not a huge loss.
-While its movepool gives it just enough options to function as a special attacker, it's still fairly predictable and lacks any way to hit Rock types outside of Hidden Power.
-All three of its abilities are very lacking and incredibly situational, so don't expect to get much benefit out of them.
-As a Boomburst user it's difficult to justify using Chatot over Exploud, who boasts much better coverage options and actual bulk at the cost of being noticeably slower.

Abilities

Keen Eye: Opponent cannot lower this Pokémon's accuracy. The Pokémon ignores evasion boosts of the opponent. If you're playing on Battle Spot this ability can be useful for the always annoying Double Team abusers, but evasion abuse is rare, inconsistent and generally frowned upon in competitive circles so it's not an ability that will get much use.Tangled Feet: Pokémon's evasion raises one level when Confused. Even with an evasion boost there's no guarantee you'll even avoid an attack, let alone break through confusion and attack. Your best bet is still to switch out when you're confused so this ability is relatively useless.
Hidden Ability (Available):Big Pecks: Its defense cannot be lowered. Moves that lower defense are almost never used so this isn't a very helpful ability. Drops from Crunch or Iron Tail are very unlikely to come into play either since Chatot isn't realistically going to survive strong moves like that in the first place.

While Chatot may have trouble finding setup opportunities, it makes for an acceptable Nasty Plot sweeper. Using a Focus Sash guarantees it can get a boost assuming it Stealth Rock isn't up, though priority can still make short work of Chatot afterwards so be mindful of potential priority users when attempting to set up. Both Boomburst and Chatter are both mandatory STAB moves, with Boomburst just being insanely strong and Chatter confusing an opponent to potentially luck its way past bulkier threats that might otherwise survive Boomburst. Chatter is also Chatot's best option for the Ghosts that are immune to Boomburst. Heat Wave is generally used in the last slot to hit Steel types that resist both STAB moves, though Substitute can also be used to shield it from status and punish switch-ins at the cost of losing the ability to hit Steels. Leftovers should also be used in place of Focus Sash when running Substitute since Leftovers recovery complements the damage used to create the Substitutes and helps keep it a little bit healthier.

Nature and EV's are straightforward, Special Attack and Speed are Chatot's only usable stats so there's no reason to not fully invest in both stats. Timid is used over Modest because something as frail as Chatot needs to be sure it can outspeed as many Pokémon as possible, and Nasty Plot will already be boosting Special Attack regardless. Meanwhile the ability choice doesn't really matter, though Keen Eye can deal with evasion and accuracy nonsense if it comes up.

Since Chatot has a lot of trouble finding chances to set up, a Choice set can be used to give it more immediate utility. Boomburst and Chatter are your standard STAB moves though given the nature of Choice items Chatot needs to be especially careful of opposing Steel and Rock types before deciding to recklessly use its STAB moves. Heat Wave lets Chatot hit those Steel types though locking it into something other than a STAB move is especially dangerous since a wary opponent can easily take advantage of a Chatot locked into Heat Wave. U-turn can be used in the last slot to gain momentum against expected switch-ins and bring in something else to handle it, though Hidden Power Ground can be used to hit Probopass and other Rock types for super effective damage. If hitting Golem and Rhyperior is more important than hitting Probopass, Grass can be used over Ground. Hidden Power Grass can also hit the likes of Quagsire and Gastrodon slightly harder than Boomburst does though you're usually better off hitting something with Boomburst in most cases anyway.

The decision between Choice Scarf and Choice Specs naturally depends on whether you want Chatot to function as a revenge killer or wallbreaker, respectively. Specs Boomburst hits hard and makes Chatot difficult to switch into directly, though with a Scarf Chatot becomes fast enough to threaten more offensive teams at the cost of a significantly less power. Once again a Timid nature and with maximum Special Attack and Speed investment should be used, as Chatot really can't make afford to invest in anything else.

Other Options

Life Orb, Encore, Sleep Talk, Tailwind, Taunt
-Life Orb can be used on the Nasty Plot set to give Chatot's moves a little more power at the cost of 10% of its HP, but Chatot isn't going to be taking hits regardless so the recoil isn't so bad.
-Encore can be used to give Chatot a free opportunity to set up by locking the opponent into an expected status or setup move. It's a wonderful tool though it can be difficult fitting it onto a moveset.
-Sleep Talk can be used on the Choice Scarf or Choice Specs set to let Chatot function as a sleep absorber, which lets it handle the likes of Vileplume and Jumpluff more handily.
-While it isn't the best user of the move, Tailwind can let Chatot support its teammates as a last-ditch effort. It can also be used to give Chatot the jump on threats that normally outspeed it and potentially beat them on its own.
-Taunt shuts down passive threats and prevents Pokémon like Grumpig and Klinklang from trying to set up, though as with Encore it can be difficult to find room to fit Taunt on a set.

Double & Triple Battle Options

Here it is! The Pokemon with the strongest STAB Boomburst, Chatot! Followed very closely by it's Scrappy Base 91 SAtk having Exploud!
Boomburst is an incredibly destructive attack with 140 Base Power and 100% to boot. The kicker is that it hits EVERYTHING surrounding the user. So very careful team building will need to take place so that you aren't KOing your own Pokemon more than you are to the opponent.

It's difficult to suggest Chatot when Exploud is readily available with a much stronger ability in Scrappy.
It only gets more difficult when one see's that Chatot has the same base speed as Landorus-Therian a Pokemon that many players are prepared to outspeed.
With that even though it's base speed is much higher than Exploud's, more than likely the opponent is faster anyway. Where Exploud could take a hit or two before being KOed Chatot really cannot take a hit without severe consequences.

Things only go downhill when one realizes that Ghosts won't mind non scrappy Boombursts. Exploud's Scrappy Boomburst will ALWAY damage an opponent who isn't protecting/protected. Shoot, Pixilate Hyper Voice is only blocked by Soundproof Pokemon, and can even hit for Super Effective Damage.

This leaves Chatot feeling very small and outclassed, there is the Ground Immunity to be happy for. Going the Boomburst route will get CHatot nowhere Exploud or even Noivern could do more effectively. Time to look at its signature move - Chatter

Chatot's non Boomburst focused set will abuse Chatter's 100% confusion rate alongside being disruptive support. Encore is generally always disruptive and kind of combos with Tailwind, as fast Encores are hard to deal with. The last slot is dependent on if you want to preserve Chatot, hurt the opponent, or annoy the opponent some more. In some cases you may be able to disable the opponent entirely with Encore + Torment. Boomburst is secondary STAB and will hurt the Electric Types who resist Chatter.

Partners for Chatot may want to be Soundproof to avoid Boomburst Damage, so Mr. Mime is a prime candidate for that. It even has Fake Out and Helping Hand. Even when Timid, a Helping Hand Boomburst is no joke.

Chatot is severely outclassed on many fronts, having the strongest Boomburst isn't that valuable when common pokemon like Gengar and Aegislash dodge it entirely. Not to mention the strain put on Team Building when considering Boomburst. Until Chatot is able to take a few hits or provide more than just stronger Boombursts than Exploud, it's a good idea to avoid using it.

Countering Chatot

As one might imagine Chatot isn't particularly hard to counter, though Boomburst and Chatter can make it a nuisance to switch into if you aren't careful. While Steel types don't like Heat Wave, Rock types in general can handle Chatot with no problems outside of the occasional Hidden Power. Probopass, Golem and Rhyperior in particular are an incredibly solid stops to Chatot, fearing nothing except Hidden Power while KO'ing back with their respective Rock STAB or getting a free opportunity to set up Stealth Rock. Ghosts like Mismagius, Jellicent and Dusknoir are immune to the dangerous Boomburst so they make for relatively safe switch-ins, although they have to rely on coverage and not getting confused to death by Chatter. Plain old Rotom combines the best of both worlds by being immune to Boomburst, resisting Chatter and easily picking it off with Thunderbolt. Fast Electric types like Raichu and Scarf Rotom-Frost also have no trouble revenge killing Chatot, though really anything faster than Chatot should have little trouble taking it out. By extension, all common priority moves can make short work of it due to its nonexistent bulk. On the more defensive side of things, dedicated special walls like Lanturn and Lickilicky can handle the Choice set though they still have to be cautious around the Specs set and Nasty Plot variants, particularly those running Taunt. The bad news just gets worse once the big guys get involved, though. Tyranitar and Heatran have no issues shrugging off anything Chatot can do, and even with the proper Hidden Power it isn't doing much of anything without a boost. Bisharp, Azumarill, Talonflame and Scizor demolish the poor bird with their respective priority moves, and the high speed tiers mean that Chatot can't even begin to compete with many of the game's biggest threats. The huge amount of dangerous Steel types also makes it difficult to repeatedly fire off Boombursts, so Chatot often finds itself at an unfortunate loss. Chatot might have some cute moves at its disposal that prove to make it a nuisance, but as long as you aren't careless you shouldn't struggle too much if you ever come across this little parrot.